So I’m running two 3s lipos in series. I charged both of them a few times individually, then I bought a 3s to 6s connector so I could charge them as a 6s battery. I charged them this way several times with no issue. The other day I plugged in the power leads to my charger, then while plugging the second balance connector into the 6s adapter, I got sparks and melted the shit out of the connector. Without any doubt I plugged it in the correct direction, and even backwards I don’t think the key allows any contact between wires. I couldn’t salvage the connector, so I cut the wires and soldered the 6s connector directly to the two batteries, charged no problem. When they were full I put them back on my board, plugged the power wires into my series adapter, more sparks and fire, also plugged in the correct direction. I cut the balance connector off, and now my board is running like its supposed to.
No idea wtf is going on. Internal short in one of the batteries maybe? I can’t find anything wrong with my adapters, and they worked like they were supposed to for several months.